Direct broadcast satellite (DBS) signals are often transmitted to aircraft and other moving vehicles. These transmitted signals are often KU-band television signals that are transmitted to commercial aircraft, trains and other moving vehicles, and are typically UHF and VHF band signals, which can be received on small antennas, such as the common 18" disks placed on the sides of houses. The antenna can also be formed as a phased array antenna, and designed as a flat plate, as is known to those skilled in the art. Many different types of housings and positioners have been designed to point the antenna's main beam at the desired direct broadcast satellite while an aircraft maintains various commercial cruise flight dynamics. These dynamics include a role of 5.degree./second and 5.degree./second.sup.2 ; a pitch of 5.degree./second and 3.degree./second.sup.2 ; and a yaw of 5.degree./second and 5.degree./second.sup.2.
One current method has been to use a mechanical device with an in-line jack screw actuator for elevation and a direct drive azimuth. In most types of controls, an antenna controller receives position commands and directs movement of various motors. However, these type of requirements are not adequate because with a mechanical system, the slew rate is slow and motors often overheat in maintaining positions. Also, the controller does not include a rate feed forward, which is desirable. Also, many prior art antenna positioners have mechanical designs that allow control over azimuth and elevation, but the motors and drive mechanics have excessive backlash. Also, many prior art designs do not fit into low profile housings that are adapted for mobile applications, such as mounting on the fuselage of an aircraft.
U.S. Pat. No. 5,025,262 to Abdelrazik et al. discloses a pedestal with a helical element antenna that is mechanically steered with reference to an azimuth axis and elevation axis. A mechanical steering system includes a supporting frame having an azimuth member and an elevation member that is integral with the azimuth member. It includes a longitudinal axis displaced from the azimuth axis.
U.S. Pat. Nos. 5,689,276 and 5,420,598 to Uematsu et al. disclose an antenna housing for a satellite antenna device, which mounts on a moving body and includes an automatic tracking mechanism. An elevation motor is fixed to a rotary base. A series of pulleys and shafts act as a driving mechanism. A rack has teeth formed along a circle about the rotating axis in elevation direction of the antenna unit A. The teeth of the rack mesh with the pinion gear to be driven circumferentially by the driving torque transmitted to a pinion gear. Thus, the antenna unit is driven for rotation in the elevation direction. An azimuth motor is fixed on the rotary base. Through a sufficient pulley mechanism, the driving torque of the azimuth motor is transmitted to the pinion, which meshes with teeth of a belt such that the driving torque of the azimuth motor is transmitted through the pulleys.
U.S. Pat. No. 5,153,485 to Yamada et al. discloses a high gain antenna that is mounted on board an automobile for reception of satellite broadcasting. The system uses a beam antenna in the form of a flat plate that is secured to an antenna bracket. A turntable has a disk-shaped spur gear that includes a gear around its lateral side. Turntables are rotatably mounted on a stationary base by a bearing. Reduction gearing in a motor is mounted on the support plate and secured to a stationary plate base. The beam antenna can be moved in both azimuth and elevation.
Many of these systems suffer some of the drawbacks noted above.